This invention relates to particulate inhalers and, in particular, to a mouthpiece for such an inhaler, the mouthpiece being provided with means for ensuring that the particle size of the entrained medicament is minimized.
Mouthpieces for inhalers in the prior art have used many different means for breaking up the particulate medicament which is being inhaled by the patient. Such means include the use of staggered teeth, baffle plates, filters and stationary helical devices.
In particular, as disclosed in WO 98/41264, it is known to provide a rotatable member within the mouthpiece, the rotatable member having a number of angled arms with which entrained medicament may collide during operation of the inhaler.
A disadvantage with such an arrangement is that a rotatable member will spin with the air flow which reduces both surface effects and also the likelihood of any impact of the medicament with the rotatable member, as some particles can travel undeflected through the mouthpiece. The airflow causes the arms of the rotatable member to rotate out of the path of the particle and, thus the arms, rather than the particles, gain rotational energy such that the particles experience a reduced acceleration and shear. Further, a rotatable member is more susceptible to friction at the points at which it is mounted within the mouthpiece. Furthermore, the performance of the rotatable member will be adversely effected as the speed at which it rotates increases. The present invention is directed to providing a mouthpiece for use in an inhaler for particulate medicament to break up agglomerations of particles and which overcomes the above problems.
According to the present invention, there is provided a mouthpiece for use in an inhaler for particulate medicament, the mouthpiece having:
an inlet and an outlet for particulate medicament;
a helical member disposed between the inlet and outlet for, in use, imparting a rotational movement to an air flow which is drawn to the mouthpiece and in which medicament is entrained;
wherein the helical member is, in use, axially movable between a first position and a second position such that it restricts the build up of medicament on the inside of the mouthpiece.
Thus, the helical member, which may scrape the inside of the mouthpiece or which may have its radially outermost part adjacent an inner side of the mouthpiece, clears deposits of medicament on the inside of the mouthpiece. Furthermore, as the axial movement of the helical member introduces an acceleration and a vibration to the helical member, particles which adhere to the surface of the helical member may be dislodged.
Thus, the present invention provides a non-rotating member, the performance of which is not adversely effected by loss of performance due to rotation. Thus, the present invention clears depositions of particulate medicament without sacrificing the energy which is required to rotate the rotatable member of the prior art.
Preferably, the mouthpiece further comprises biasing means for urging the helical member towards the inlet to the mouthpiece.
The biasing means may be a pair of resilient arms attached to the helical member, preferably at one end thereof.
The helical member may have a plurality of intertwined helical sections, preferably two.
Preferably, the helical sections each complete at least one revolution.
Preferably, the movement of the helical member Is caused by the airflow drawn through the mouthpiece, in use, by the user.